1. Field of the Invention
The present invention relates to a mechanism for fine adjustment of the orientation and/or the position of a payload, the mechanism being suitable for subjecting the payload to very small rotations and/or displacements.
2. Description of the Related Art
In the state of the art, small value rotations and/or displacements of a payload are obtained:
either by using systems with bar linkages suitable for reducing displacements (four bar linkages are conventional, or even six bar linkages for more complex systems);
or by using contacting pieces that move relative to one another over skewed surfaces that slope relative to the reference axes of the adjustment mechanism;
or else by using plane membranes including cutout zones that modify their deformation properties.
The work "Antenna pointing mechanisms handbook" (by L. Paratte, May 1988, Estec W.P. 1517) describes what may be considered as the best fine pointing mechanism that is available in the state of the art, enabling very small rotations of the payload to be obtained with an accuracy of two thousandths of a degree over a range of .+-.1.5 degrees, with these mechanisms being known under the reference Matra APM-PA.
However, mechanisms for obtaining fine adjustment of the orientation of a payload do not enable coarse adjustments to be obtained and they are essentially designed to operate within fixed and predetermined positioning ranges.
An accurate mechanism for displacing a payload, as developed by Dornier in West Germany, is also known. That mechanism is illustrated in FIG. 1 accompanying the description of the present invention. It may be observed that it includes a circularly symmetrical resilient component 1 constituted by a discontinuous (or open) resilient ring whose opposite bottom ends 2 and 3 are connected firstly to two actuator levers 4 and 5 which are inclined relative to the vertical, and whose lines of action pass through the center of the resilient ring, and secondly by a leaf spring 6 fixed to a shaft disposed in the center of the ring 1 and interconnecting the two ends 2 and 3 in such a manner as to direct the deformation of the ring 1 when the levers 4 and 5 are actuated to move towards each other, and in particular to direct the deformation downwards: in the Dornier device this is obtained by acting on an axial piece 7 (in the direction shown by the arrow), which piece is connected to the levers 4 and 5 via two auxiliary levers 4a and 5a. The resilient ring 1 can thus be deformed in such a manner that its diameter is reduced in the vertical direction by an amount s, as shown in FIG. 1, where the top of the ring 1 is shown as moving downwards when the two levers are actuated, thus obtaining downward deformation given the stress imposed by the leaf spring 6 which serves specifically to direct the deformation in the said direction.
However, it should be observed that in the Dornier mechanism:
it is possible to obtain translation movements only, rotation is not possible;
the open circular ring is deformed by means of actuator levers because of the two opposite ends of the ring moving towards each other under the control of the leaf spring; and
the deformation force is not applied directly to the resilient ring but is applied via a lever system whose purpose is to provide a first displacement reduction.